Precast sleeper construction



Oct.

C. LE R. OLSON PRECAS'I' SLEEPER CONSTRUCTION Filed Jan. l5, 1953 fliThis invention relates to a precast sleeper construction of the typewherein rot proof sleepers of mineral characterv are bonded to anunderlying concrete slab, such sleepers being nail-penetrable so that awood flooring can be nailed thereto.

Sleepers are extensively used in connection with floorings wherein thebase is a concrete slab. In such construction it is conventional toprovide a concrete slab, to a'x sleepers thereto inv spaced, parallelarrangement, and to nail a wood flooring to the sleepers. Such sleepersmay be of wood construction suitably bolted or otherwise afxed toconcrete slabs. Wood sleepers, however, are disadvantageous for severalreasons. Thus, they are combustible and are subject to the ravages oftermites and dry rot.

For these and other reasons, so-called concrete, cement or compositionsleepers of a mineral character are used extensively. Such sleepersshall be referred to hereinafter as concrete sleepers.

Concrete sleepers are not combustible and are termite and rot proof. Forthe purpose described, the composition of concrete sleepers must be suchthat, when it has set 'and cured, it will have adequate strength for theload to be imposed upon it. It is also necessary that the sleepers besecurely fixed to the underlying slab and that they be penetrable bynails. The sleepers must have a satisfactory nail-holding power so thata wood llooring nailed to the sleepers will be held securely.

Compositions of this character are well known and re. quire no detaileddescription herein. Typical compositions are set forth in the followingpatents: Smallman, l,651,0.76; Wires, 1,860,917; Atterbury, 1,163,060,and Taylor, 1,302,452. The Atterbury and Taylor patents describeconcrete compositions in which the cementing agent is Portland cement,whereas Smallman and Wires relate to so-called magnesite or Sorelcements wherein the cementing agent is a mixture of magnesium oxide andmagnesium chloride. In a typical composition of this type, magnesia in asuitably comminuted state `and a suit.

able filler material or aggregate such as silica or limestone dust laremixed with sawdust, wood liber or asbestos. To this mixture, just priorto casting the sleeper, is added a magnesium chloride solution, usuallyabout a 22 B. solution. A reaction ensues between the magnesiumchloride, magnesia and Water. The cement is of the hydraulic type. Thewet mortar sets rapidly and, inthe course of time, cures to provide amonolithic mass which has the necessary strength to support a woodflooring,

which bonds satisfactorily to ya variety of materials in cluding slabsof ordinary Portland cement concrete,.

which is nail-penetrable and which has a satisfactory nailholding power.

Heretofore, owing to certain difliculties in the use of precastsleepers, it has been the practice to cast such sleepers in situ.sleeper construction but, for various reasons, it is cumbersome andleaves much tovbe desired. Thus, this type of This practice provides asatisfactoryv States 1 atent operation i. e., casting in situ) requiresthe use of relatively expensive and very heavy steel forms. The formsmust be supplied to the job and must be laid out and leveled. oit flushwith the tops of the forms, yand 'afterthe cast sleepers have set, theforms must be removed. The

forms must then be cleaned and oiled, then transported-' to the nextjob, or to a central storage place if there h apf. pens to be no jobrequiring them 'at the time. The singlel ltem of cost of transportingforms to and from a job is itself a substantial factor. Also, thispractice requires that 'a construction crew be provided at each andevery job who are skilled in handling the forms, the preparation of themortar, the casting and finishing operations and removal of the formswithoutdamageto the sleepers.

The employment of precast sleepers is an attractive alternative tocasting sleepers in place. Thus, precast sleeper sections can be made ata central plant with proper equipment and by a skilled crew of workmen.The sleeper sections can be finished to precise dimensions, tied to'gether in bundles and delivered to a job in predetermined lengths.Whenever it is necessary to employ a short sleeper section, e. g. at theen-d of a string of sleepers, it is a simple task to cut o-r saw asleeper section of predetermined length to the required sho-rter length.

Notwithstanding these apparent' advantages the employment of precastsleepers has been retarded for certain very practical reasons. As hasbeen mentioned above, nail penetrability is an important property ofsleepers of the character referred to. Of course, precastnail-penetrable sleepers offer no problem per se. However precastsleepers must be securely bonded to the underlying slab. Frequentlythere is unevenness in the top surface of a concrete slab, with theresult that lthe layer ing the precast sleeper to the slab must be ofvarying thickness. If this layer of bonding cement of varying thicknessis not n-ail-penetrable, difficulties will be encountered in nailing awood flooring to the sleepers. Thus, where a relatively thin layer ofbonding cement is inter. posed between the under surface of 'a sleeperand the upper surface of the concrete slab, and if this layer of bondingcement is not nail-penetrable, diiculty will be encountered in driving anail into the sleeper Iat such location.

Another diiculty arising from the uneven character o f concrete slabs isthe necessity of providing sleepersof varying thickness. Thus, becausethere are low spots, highV spots and intermedi-ate areas on slabs, it ispresent practice to provide extra thick sleepers, extrathin sleepers andsleepers of average thickness.

It is also desirable to provide a suitable bonding cement" which is notonly nail-penetrable but whichwill serve to bond the precast sleeperssecurely to the concretesl'ab" and which will set rapidly.

Another difficulty encountered in the employmentof, precast sleepers isthe fact that the top surfacesofl con'- crete slabs vary in texture.Thus, one slab may have a smooth surface whereas another slab may have'a very rough surface. It is more -diicult to bond a sleeper securely toa smooth slab than to a rough slab. f

It is an object of the present invention to provide improved means oflaying sleepers on and bonding them to concrete slabs and the like.

It is a further object to provide `an improved method of,

laying precast sleepers on and bonding them tov a concrete slab.

Itis aparticular object of the invention to provide Nan Patented Oct.2,1956

After the mortar has been poured in and struck.

of cement bond- 3Y wherebytlie' finished job Willpresent an upper slabsurface lying'irr apredetermined 'horizontal plane.

Yet another object is to provide a cementing composition which isadapted to cement and bond precast sleepers securely taconcrete'slabs'.f

Another object is to provide arneans of applying precast concretesleepers to uneven slabs withoutthe necessityot`"'emplf` ying,r morethan one size of' sleeper.

Yet another andv particular object isY to provide a cementing orbonding`composition which willsecurely and'. rmiy bond nail-penetrable;concrete sleepers to a concrete"A slab; and which, upon, setting, isitself nail-penet1'atile:r

[liese-andother objects of the invention' willi be apparent` from theensuingdescription and' the appendedl claims:

Oneformiof the invention-is illustrated by-Way of ex. ample in theaccompanyingdrawing in" which,

Eigure` l is'a perspective viewV of a concrete slab, illnstrating' the;initial stages in the laying of sleepers in accordance' with ,theinvention,

Figurelis a similar view showing the iinal stages ofl laying sleepers inaccordance with the invention, and

Figure 3, is a fragmentary, longitudinalsection taken through a sleepershowing one Way in which the cementing agent ofthe invention is alsoused as a filler.

In accordance with the present invention, I. provide precast' sleepersof suitable composition, which are of mineralcharacter,l which arenail-penetrable and which are rot-proof. I then prepare the surfaceofthe slab in." the manner more fully described' hereinafter. I thenapply to the slab strips of a suitable nailpenetrable cementgrsuchcement beingcapable, uponsetting and curing,v ofbonding the sleepers tothe slab. In carrying out thisV application of cement, I observevcertain precautions and'` fllowa certain technique as more fully setforth hereinafter. I then lay the precast sleepers, over the cementinend-,to-end relation and allow the same to setand cure.V

The, sleepers4 used in accordance with the-present invention maybeof'any suitable composition and construct tion,v e. g., a dry mix maybe provided consisting of 25% magnesia,.12%, coarse.sawdust,j26%limestone dust and 37%' white sand, suchpercentages beingby weight. ToYthisdry. mix.is added 22T B. aqueous magnesium chloride solution inquantity suliicientto provide a plasticmassi which` caribe troweled.Sleepers. may. be made. from the resultant wet mix by any desiredmethod. Prefeerably anrapparatus and a method. are-employed which aredescribed Y. and` claimed in my co-pending ap plication. Serial No.291,195., tiledJuneZ, ancltAppa'ratus` for Forming Cementitious. Slabs.

Asx-describedginthe` aforesaid co-pending patentr applil.- cation, thewet mix is placed' in asteel formlined. with; waxpaperandhavingYuprightzsdes and ends. The depth oithis'v frmfis; substantially the,desiredthickness ofV the` sleeper. 'llhe ends of the formV are, formedlwithk slotst spaced'apart the width of the sleepers. Thus;A the formmay, have an overall width tive times'the width ofV a sloepen and theends slotted` at appropriate intervals.

The' form isA then placedin a'press and the slab con-- tained therein issubjected to simultaneouscompression4 and" agitation to compact' it;Thenr theform` is passed underneath a setof rotary=knivesorblades'which'are in registry with the slotsformed' in the endsf oftheformt" The rotary knives' are preferablyy set' tol clear therbottomoftheform byasmall fraction of anY inch: A- singl'epass; under therotary knives sufhcestocut the-slab-into'sev-4 eral; e: g., 've;individual sleeper sections'- which, however; are' joinedat'theC bottomby a thickness off' cementcorresponding to the knife clearance.

Arr' inverted steel1 channel of`substanti`ally the same asA the form' isthen` provided andI isf-'covered withwarpaperf The-"formisup-endedandthe-sl`abwithin dumped ontcr the channel; Thel wax` paper' used?lfor- 1952, @mined Method f lining the form is removed and the channelwith the fresh slab is placed` on a rack to allow the slab to set andcure.

The set slabs are then removed and stacked. When ready for use, theindividual sleepers are easily detached by hand; i. e., one sleeperbreaks away from the adjoining sleeper because of the very smallthickness of cement joining them.

It willbe apparent that the.` apparatus and technique thus employed tomanufacture sleepers lends itself to speedy operation andhigh productionrates, and that the sleepers-are of uniform ,size and configuration.-However, such apparatus and technique require use at a central'plantrather than on theA job,` to operate efficiently. It will, therefore, beapparent that apparatus and technique are available to manufactureprecast sleepers economically.

The precast sleepers so constructed may be of any suitable length, Widthand thickness, e. g., 5 ft. in length, 21A inches in width and l/s`inchesA in thickness.

'Ille cement employed inaccordancewith the present inventionmay be anynail-penetrable cement which will bondto the precast sleepers and toconcrete slabsy and; which is rot-proof. Preferably an Oxy-chloridetype. of cement is employedinwhich the filler is of a nature suchl thatthe cement, after setting and curing, is nail-.penetrable. Anexample ofa dry mix employed to preparel thepreferred cement is as follows:

MgO'l 25 f Coarselsawdust e 12'-V llimestone dust 26;

Minus SO-rnesh Del Monte (California) white sand-- 37 Total' 1GO y pletedry mix may lne-employed including. the; magnesium.V

chloride. component. lnesuch case-the magnesium c1110.-- ridecomponentmay havebeen pretreatedto provide it` with; a protective. coating,`suchv as that described` in my ca -pending. patent application SerialNo. 319,003, entitled; Coatedf Hygroscopic4 Material and Method ofMaking; Sameg hled November 6; 1952.. Whenever a complete; dr'yrmixofthis character is` employed, water instead of: theimagnesiurn chloridesolutionwillbe employed, being: added to'the. completedry'mix just priorto its ,utilization` Instead ofa magnesium Oxy-chloride type offcement,a" Portland cement type-V mayA be used, in which Portland'` cement isused in placent magnesia and a-dilute aqueousf calcium` chloridesolution isused in place of: magnesium chloride solution'.Y

TheA slabr is prepared"as1follows:V In new construction4itfislpreferably-tospecify that theslab shall have `a rough texturedsurface, which can be achieved by.A redding, grooming'or heating. Suchafroughened surface -provides a-better bond" between the cement andtheslab. How--A ever, the=method and material of' my-inventionareiapplicable to a smooth slab as will appear moreefully herein? after;- Thesla'be is suitably` cleaned and freed, of.,` all foreign matter.y Thenchalk;1ines are snappedrontothe: slabat predetermined centers, e. g;,.1,6 inches apart.` If; theslab Ahas1a,roughenerl surface; itispreferabletorbrush'; al-` suitablegroutf along the chalk" lines'. and;approximately;

the width of the sleepers. A suitable grout can be prepared with amixture of one part by weight of seawater magnesia and one part byweight of white marble dust or limestone dust. Immediately prior to theapplication of the grout, a 22 B. aqueous magnesium chloride solution isadded to and mixed with the dry grout mixture, in quantity sufficient toproduce a mortar of approximately the consistency of pancake batter. Thecement should be applied to the grouted surface and the sleepers set inplace before the grout hardens. The grout ensures a good bond betweenthe slab and the cement.

Should the slab be smooth it may be roughened along the chalk lines byany suitable means and then grouted as described above. Alternatively,nails may be driven in and their heads allowed to project above thesurface of the slab. For example, concrete stub nails may be driven intothe slab 4 apart, and their heads allowed to protrude approximately 1A"above the slab. Alternatively Olson Masti-Dek or Olson Bond Grip may beapplied along the chalk lines and allowed to harden before application.of the cement. Olson Masti-Dek and Olson Bond Grip are trademarks ofLeRoy Olson Company, San Francisco, which are applied, respectively, toa black or colored, coarse-grained adhesive, and to the same productcontaining Portland cement.

When the slab has been thus prepared, a nail-penetrable cement capableof bonding to the sleepers on the one hand, and to the treated slab onthe other hand, is employed. In this connection it is usually necessaryto lay the sleeper sections so that their upper surfaces are at apredetermined height above the slab. Assuming, for example, that theslab is perfectly level, that the upper surface of the sleepers is to be1% above the slab and that the sleepers are 13/8" thick, it will beapparent that a layer of cement 3/8" thick will be required.

Referring now to Figure l of the drawing, a concrete slab is shown at10. This slab will have been swept clean, chalk lines 11 are snapped onat predetermined centers, e. g., 16 inches apart, and the surface alongeach chalk line will be suitably roughened, if necessary (or nails willbe driven in). In Figure 1 the preliminary stage of laying sleepers isshown. Thus, along each eighth chalk line the surface of the slab willbe grouted or otherwise treated as hereinabove described, to promote asecure bond to the slab. Then along each such eighth chalk line, a stripof nail-penetrable bonding cement will be applied. Two such strips ofcement are shown in Figure 1 and are indicated as 12. Individual precastsleeper sections 13 are laid end-to-end along each such strip of cement.To properly gauge the thickness of the cement strips 13, a water levelor engineers level may be employed, and a long straight edge may then belaid along the string 14 of sleeper sections. Alternatively, soft stoolsof the cement (not shown) may be laid along the side of each eighthsleeper at five or ten foot intervals and levelled, with the aid of awater level or engineers level, at the predetermined height of thesleepers. Such stools will serve as a gauge in levelling the sleepers.Excess cement will be struck from each eighth sleeper, as it is laid andlevelled, and this excess cement can be gathered up and used for thenext sleeper.

Referring now to Figure 2, on the following day, or as soon as thecement has set sufciently, the intervening sleepers 14 are similarlylaid along the intervening chalk lines 11, after suitable preparationwith grout or otherwise. In this final stage, leveling of theintermediate sleepers can be accomplished very simply by means of a longstraight edge such as that shown at 15. The straight edge 15 is laidacross the previously laid sleepers, which therefore act as gauges forleveling the great majority of sleepers.

In all cases, of course, when a sleeper is laid and set to level, andbefore the cement sets, excess cement will be struck from the sides ofthe sleeper and used again. Thus it may be gathered up and mixed withfresh cement.

uneven and in many cases the unevenness is substantial.

' In this rconnection an important advantage of the technique and thecomposition of the parent. The composition of the invention is referredto for convenience as a Vcementf However, it serves not only as acementing or bonding medium to bond sleepers to a slab, but also servesas a ller to accommodate variations in level of the slab. Thus, ingeneral where there are depressions or low spots in a slab, a greaterquantity of cement will be used to iill such low places. Conversely,where there are high places in the slab, correspondingly less cementwill be used.

In this connection it should be noted that the chief advantage of thepresent invention is that it provides a more practical means ofemploying precast sleepers. In the event that the surface of a slab ishighly irregular or uneven and includes excessively high spots or humpsand excessively low spots, it has been the previous practice to employextra thin sleepers (to cover high spots), extra thick sleepers (tocover low spots) and sleepers of intermediate thickness for portions ofthe slab which are at an average or intermediate level. Accordingly, andas illustrated in Figure 3, a variation of the technique described aboveis employed. Referring now to Figure 3, a portion of a slab 10 is shownin cross section which includes a high spot or an exceptionally highconvex irregularity at 10a, and a low spot or exceptionally concaveirregularity at 10b. As illustrated in Figure 3 the sleeper sections 13adjacent the high spot 10a are spaced apart to provide a gap 15therebetween. This gap is filled with the cement or filler material ofthe present invention, which is struck off so as to be iiush with theupper surface and sides of the adjacent sleeper sections 13. A illersegment 16 of nail-penetrable cement is thus provided. By this means,continuity of the sleeper 14 is preserved, only a small amount of cementis needed for the purpose, the ller segment 16 is securely bonded to theslab and to the adjacent ends of the sleeper sections 13, and thissegment is nail-penetrable. As is also shown in Figure 3, the cement isemployed-as a filler for a low spot such as that shown at 10b. It will,therefore, be apparent that only one size of sleeper is necessary.

Among other variants which may be mentioned are the following: Thetechnique and materials of the present invention may be applied to oldor new slabs. As stated, the slab is preferably provided with aroughened surface, and where the present invention is applied in newconstruction, the supplier should specify that the surface of slab beprepared rough, e. g., with a rodded or iloated nish. The technique andmaterials of the present invention are applicable where sleeper sectionsare laid in endto-end, abutting relation and also where they are spacedapart at their ends for purposes of ventilation. The invention is alsoapplicable where the spaces between the rows of sleepers are filled insolid with concrete, e. g., where re hazards, a lire ordinance or heavyloading of the floor so requires. In such a case it is preferable toapply a seal coat of asphalt to the entire surface of the sleepers (topsand sides), before filling the spaces between sleepers. The presentinvention is equally applicable to so-called spring oors, such as usedin dance halls, gymnasiums and play rooms, and to more solid iloorslacking the quality of springiness.

I claim:

l. A method of sleeper construction wherein a plurality of rot-proofconcrete sleepers are aiixed to a concrete slab or the like at spacedintervals along predetermined centers, said method comprising, as aninitial step, applying to said slab along a minor portion of saidpredetermined centers strips of cement capable of setting to provide ahard, non-plastic nail-penetrable, rot-proof bond between the slab andthe sleepers, such initial step present invention is apleavingra.majority/fot; intermediate; .uncemented .predetermined: centers,.layingsleeper; sectionsin end-,to-end relation along such .cemented strips,bringing .suchrsleeper sec-v tionstoza. predetermined level `andallowing the cement to set; then, as asubsequent step, similarlyapplying cement.

mined centers, applying .to the slab along a minor portion. of saidguide lines strips; f. nailfpenetrable, rot-proof cement capableofzsettingto ahard, non-plasticmass and of bonding to the slab. and'. tonailpenetrable concrete.

sleepers, such .application being vcarried out so as.:to leave amajorityof. intermediatelguide linessuncemented, provid ing aplurality ofindividual concrete, rotpro0f,sleeper sections eachofrelatively shortlength compared tothe lengthV ofl an; entire sleeper, laying suchsleeper sections.

in end-to-end relation along the. cemented strips, leveling the sleepersto a predetermined level and allowing thev cement to set; then similarlytreating the slab along said intermediate guide lines;with suchcement,laying the re mainder: of the sleeper sections. along the resultingvcemented strips, and :employing thepreyiously laid sleepersl as gau gesyto level. the subsequently. laid. sleepers.

3. In the method otsleeper. construction whereinnailpenetrable concretesleepers are bonded. toa nailimpene-y trable yconcrete slab inspaced,parallel arrangement along predeterminedcenters, such;slab. havinganon-uniform.

surface including low spots, theimprovement which comprises: applyingguide linestothe slab.. along said prede.-

termined centers,L applying: to a minor. portionof. said` guide linesstrips of nail.penetrable,. rot-proof cementA capable of setting Yto ahard, non-plastic mass and of bonds. ing to the slab and to thesleepers, such'application.being` carried .out to leave a majorityof.uncemented intermediate guide lines, providing a plurality ofindividual sleeper sections of nail-penetrable, concrete, composition,laying' such sleeper sections inl end-tofend relation along the cementedstrips, leveling such sleeper sections, employingV saidLcernent as afiller for said low spots, and allowing .the4 cement to set; thensimilarly applying strips of said cement tothe-slab .-along, saidintermediate. guide lines and layingv suchsleeper sections. thereon,meanwhile employing the previously laidsleepers as gauges to` level thesubsequentlyl laidt intermediate sleepers..

4. A.method of sleeper construction wherein sleepers are. afxed toanail-impenetrable concrete slab having an irregular` surfaceincludinglow spots and high spots, such methodcomprising: applying to the slabspaced, parallel guide lines along.v predetermined centers, applying toa minor portion of said guide lines a nail-penetrable, rotproof cementcapable of setting to a hard, non-plastic mass.- and ofv bonding. to theslab and to concrete, nailpenetrable. sleepers,meanwhile leaving amajority of uncemented intermediate guide lines, applying individualsleeper.sections to the. strips of cement, providing a supply of..nail-.penetrable, rot-proof concrete sleeper sections, applying. suchsleeper.. sections tothe cemented strips in endatofend relationtoprovidea plurality of continuous sleepers, bringinglsuch' sleepers to apredetermined level and employing suchcement to lill low spots, to coverhigh spots and'to providean average thickness of cement, spacing4v suchsleeper sections apart at excessively high spotsexceeding,.theaveragethickness of cement to provide gaps in registrywith such excessively high spots, employing said cement as a filler forsuch gaps to provide continuity of sleepersand allowing the cement toset; and then similarly applying cementV andv sleeper sections to theslab along saidintermediate guide lines, meanwhile employing thepreviously laidsleepersas gauges to bring the subsequently laid. sleepersectionsto said predetermined level.

References Cited in the tile of this patent UNITEDSTATES PATENTS

